Gigantosaur

The origin of the creature known as Gigantosaur remains a mystery. It first arose from the ocean, where it is known to live. Nuclear tests at sea may have spawned it, or it could be the result of waste-dumping, or some other toxic mutation. Dr. Atom believes Gigantosaur originated on Kaiju Island, perhaps further mutated by exposure to unknown elements.
Whatever the case, Gigantosaur has menaced various coastal cities and communities since its first appearance some twenty years ago. On different occasions, the creature has fallen under the influence of rogue Atlantean elements, or Sub-Terrans like the The Terra-King or the Serpent People, who have turned it into a living weapon against the surface world.
Gigantosaur looks much like a gigantic tyrannosaurus rex, some 120 feet tall, with a vivid purple hide capable of resisting even military grade weapons. It swims using its powerful hind legs and sweeps of its massive tail. On land, it stomps most obstacles flat, smashes them with its tail, or crushes them in its powerful jaws.